MMIC double-balanced mixer

Abstract

A double-balanced mixer for high-frequency signals includes a quad of four cold transistors in an in-line configuration, to the center of which a signal RF to be processed is fed and to each end of which a signal RF/ 2 whose phase relative to the signal RF is 180° is applied, and 180° couplers at the quad input and output. The mixer is designed to be implemented in the MMIC technology and to operate in the L, S, C, X or Ku band.

There is claimed:  
     
         1 . A double-balanced mixer for high-frequency signals including a quad of four cold transistors in an in-line configuration, to the center of which a signal RF to be processed is fed and to each end of which a signal RF/ 2  whose phase relative to the signal RF is 180° is applied, and 180° couplers at the quad input and output.  
     
     
         2 . The mixer claimed in    claim 1    wherein said quad comprises two groups of two transistors connected by their drains, said two transistors of different groups at the middle of said row are connected by their sources, a point common to said two sources receives said signal RF to be processed, the sources of said two transistors at the ends of said row each receive a signal RF/ 2  whose phase relative to said signal RF is 180°, and intermediate-frequency signals IF and IF obtained by processing are supplied at the connection between said drains of said two transistors of each group.  
     
     
         3 . The mixer claimed in    claim 1    wherein said radio-frequency coupler includes three drain-source 180° couplers forming a group comprising an input coupler and two output couplers adapted to supply a radio-frequency signal RF to said quad at a first output and two signals RF/ 2  whose identical phase relative to said signal RF is 180° at two separate other outputs which are interconnected, said signals are obtained by selectively summing signals obtained at the output of two output couplers of said group which each receive a respective one of said signals with a relative phase of 180° supplied by said input coupler, via the drain and the source of a transistor, from a radio-frequency signal supplied to said input coupler and fed to the gate of said transistor, said two output couplers are disposed so that the drain of a first coupler and the source of the second coupler are grounded, in each case via a resistor, and the source of the first coupler and the drain of the second coupler are each connected via a resistor to the same potential, which is of negative polarity for the first coupler and of positive polarity for the second coupler, the radio-frequency signal appearing at the source of the first of the output couplers is combined by a capacitive connection with the radio-frequency signal appearing at the drain of the second of said output couplers to constitute said signal RF, and the respective radio-frequency signals appearing at said drain of said first output coupler and at said source of said second output coupler are distributed to two outputs which each supply a signal RF/ 2  and which are interconnected for electrical balancing.  
     
     
         4 . The mixer claimed in    claim 1    wherein said 180° couplers for inserting and extracting said signals RF, RF/ 2 , LO, LO, IF and IF are connected to said quad by CPS stripline or CPW waveguide coplanar connections.  
     
     
         5 . The mixer claimed in    claim 1    wherein said quad and said couplers are MMIC devices.  
     
     
         6 . The mixer claimed in    claim 1    wherein said quad and said couplers are hybrid devices.